Microcapsule dispersion

ABSTRACT

The present invention relates to microcapsule dispersions comprising microcapsules having a capsule core comprising water-soluble organic substances, and a capsule coating which essentially consists of polyurethane and/or polyurea, in a hydrophobic solvent which consists of 50 to 100% by weight of glycerol ester oils and 0 to 50% by weight of solvents miscible with glycerol ester oils, and to a process for their preparation.

The present invention relates to microcapsule dispersions comprisingmicrocapsules having a capsule core comprising water-soluble organicsubstances, and a capsule coating which essentially consists ofpolyurethane and/or polyurea, in a hydrophobic solvent which consists of50 to 100% by weight of glycerol ester oils and 0 to 50% by weight ofsolvents miscible with glycerol ester oils, and to a process for theirpreparation.

Microcapsules are spherical particles which comprise a capsule core anda capsule coating surrounding the capsule core, also referred to as acapsule wall. Various uses are possible depending on the nature of thecapsule core. A decisive factor here for the properties is also the wallmaterial and the encapsulation process, for example in the case ofcapsules with controlled active ingredient release.

Microcapsules are used widely in carbon-free copy papers. Thus,microcapsules containing core oils comprising color formers have beenknown for a long time. The capsule walls based on melamine-formaldehyderesin (EP-A-0 026 914) or based on polyurea (EP-A-0 535 384) are formedby polycondensation or polyaddition at the interfaces of an oil-in-wateremulsion.

In contrast to the oil-in-water emulsions in which the oil is thedisperse, i.e. the discontinuous, phase, and the water is the continuousphase, encapsulation processes in which the two phases are reversed arealso known. These processes are also referred to as inversemicroencapsulation.

The earlier German application 10120480.2 describes such an inverseencapsulation. It teaches microcapsules having a capsule core comprisingwater-soluble substances and a capsule wall made ofmelamine-formaldehyde resins.

In addition, U.S. Pat. No. 5,859,075 teaches microcapsules having diolsand polyols as capsule core and a polyurethane wall which are preparedin paraffins as the continuous phase. The resulting microcapsules aresuitable as powder lacquer component. According to this teaching,water-sensitive substances can also be encapsulated by this process.

EP-A-0 148 169 describes microcapsules having a water-soluble core and apolyurethane wall which are prepared in a vegetable oil. As well asherbicides, water-soluble dyes are mentioned inter alia as capsule corematerial.

In decorative cosmetics, organic or inorganic pigments are usually usedas color-imparting constituents. As a result of their insolubility, thepigments behave largely inertly toward the other constituents of thecosmetic composition, in contrast to soluble dyes. In addition, theinsolubility of the pigments has the advantage that a lasting colorationof the sites within the body which have been treated with the cosmeticcomposition can be avoided.

However, a disadvantage of using pigment is their low color brilliancecompared with dyes.

It is an object of the present invention to provide organic,water-soluble substances, such as dyes, for cosmetic compositions in aform in which they behave inertly toward solvents.

We have found that this object is achieved by the above-describedmicrocapsule dispersions and a process for their preparation.

The capsules comprise a capsule coating and a capsule core. The capsulecore comprises at least one water-soluble, organic substance as solidand/or, depending on the preparation, as a solution in the hydrophilicsolvent. Preferred capsule cores are solutions of the water-soluble,organic substance.

For the purposes of this application, reactant is to be understood asmeaning an OH or NH₂ group-carrying compound which reacts with di-and/or polyisocyanate groups.

The basic principle of microcapsulation is based on interfacialpolymerization or addition. During interfacial addition, the substancesto be encapsulated and the reactant are dissolved in a hydrophilicsolvent in a first process step, and then a hydrophobic solvent isadded, and the mixture is processed to give an emulsion. The continuousphase of the emulsion usually comprises surface-active substances inorder to avoid coalescence of the droplets. In this emulsion, thehydrophilic solvent is the discontinuous, later disperse, phase and thehydrophobic solvent is the continuous phase. If the hydrophilic solventis water, the term water-in-oil emulsion is also appropriate. Theemulsified droplets have a size which corresponds approximately to thesize of the later microcapsules. To form the capsule wall, the emulsionis mixed with the isocyanate capable of wall formation in a secondprocess step. The reactant is able to react at the interface between thediscontinuous and the continuous phase with the isocyanate dissolved inthe continuous phase to form the polymeric film.

The third process step involves the after-treatment of the freshlyprepared capsule dispersion. Here, with monitoring of temperature andresidence time and optionally using further auxiliaries, the reactionbetween isocyanate and reactant is ended.

A hydrophilic solvent is to be understood as meaning either water orthose aqueous mixtures which, apart from water, comprise up to 20% byweight of a water-miscible organic solvent, such as C₁-C₄-alkanols, inparticular methanol, ethanol, isopropanol or a cyclic ether, such astetrahydrofuran. A preferred hydrophilic solvent is water.

Suitable hydrophilic solvents are also ethylene glycol, glycerol,polyethylene glycols and butylene glycol, their mixtures, and theirmixtures with water or the aqueous mixtures listed above. Preferredhydrophilic solvents are mixtures of these solvents with water.

According to the invention, pure glycerol ester oils or 50 to <100%strength by weight glycerol ester oil mixtures are used as hydrophobicsolvent. Glycerol ester oils are to be understood as meaning esters ofsaturated or unsaturated fatty acids with glycerol. Mono-, di- andtriglycerides, and their mixtures, are suitable. Preference is given tofatty acid triglycerides.

Examples of fatty acids which may be mentioned are C₆-C₁₂-fatty acids,such as hexanoic, octanoic, decanoic and dodecanoic acid.

Preferred glycerol ester oils are C₆-C₁₂-fatty acid triglycerides, inparticular octanoic and decanoic triglycerides, and their mixtures. Suchan octanoyl glyceride/decanoyl glyceride mixture is, for example,Miglyol® 812 from Hüls.

The hydrophobic solvent consists of 50 to 100% by weight, preferably 70to 100% by weight, particularly preferably. 90 to 100% by weight, ofglycerol ester oils and 0 to 50% by weight, preferably 0 to 30% byweight, particularly preferably 0 to 10% by weight, of solvents whichare miscible with glycerol ester oils. Particularly preferredhydrophobic solvents are glycerol ester oils, which are usedindividually or in their mixtures.

Examples of oils which are miscible with glycerol ester oils are:

-   -   hydrocarbon oils, such as paraffin oil, purcellin oil,        perhydrosqualene and solutions of microcrystalline waxes in        these oils,    -   animal or vegetable oils, such as sweet almond oil, avocado oil,        calophylum oil, lanolin and derivatives thereof, castor oil,        horse oil, pig oil, sesame oil, olive oil, jojoba oil, carité        oil, hoplostethus oil,    -   mineral oils whose distillation start-point under atmospheric        pressure is at about 250° C. and whose distillation end-point is        at 410° C., such as, for example, vaseline oil,    -   esters of saturated or unsaturated fatty acids, such as alkyl        myristates, e.g. isopropyl myristate, butyl myristate or cetyl        myristate, hexadecyl stearate, ethyl or isopropyl palmitate and        cetyl ricinolate.

Further suitable compounds which are miscible with glycerol ester oilsare silicone oils, such as dimethylpolysiloxane,methylphenylpolysiloxane and the silicone glycol copolymer, fatty acidsand fatty alcohols or waxes, such as carnauba wax, candellila wax,beeswax, microcrystalline wax, ozokerite wax and Ca, Mg and Al oleates,myristates, linoleates and stearates.

A water-soluble, organic substance is to be understood as meaning acompound based on carbon which is at least partially soluble in water.The organic substance must have a greater affinity to the hydrophilicphase than to the hydrophobic phase. This is generally ensured if thesubstance has a solubility in the hydrophilic solvent at roomtemperature of at least 1 g/l. The organic substances preferably have asolubility in the hydrophilic solvent of ≧20 g/l.

The water-soluble, organic substances are, for example, water-solubledyes, agrochemicals, flavorings, pharmaceutical active ingredients,fertilizers or cosmetic active ingredients. Depending on the thicknessof the capsule wall, which is influenced by the chosen processconditions and the amount of feed substances, the capsules areimpermeable or virtually impermeable for the water-soluble, organicsubstances. With virtually impermeable capsules, controlled release ofwater-soluble, organic substances can be achieved. Preference is givento water-soluble dyes.

The term “dye” includes here and below organic compounds or salts oforganic compounds, and charge transfer complexes of organic compoundscontaining a chromophore which has an absorption maximum in thewavelength range from 400 to 850 nm and thus gives rise to a colorimpression for the human eye (conventional dyes) and which itself mayalso emit light in the visible region (fluorescent dyes). For thepurposes of this invention, dyes are also compounds with an absorptionmaximum in the range from 250 to 400 nm which, upon irradiation with UVlight, emit fluorescent radiation in the visible region (opticalbrighteners). For the purposes of this invention, dyes are also organiccompounds which absorb light of wavelength <400 nm and deactivate it ina nonradiative manner (UV stabilizers).

The water-soluble dyes usually have ionic functional groups whichimprove the solubility in the aqueous solvent. In this connection, themodification can be carried out cationically or anionically. Suitablesubstituents are, for example, sulfonic acid, carboxylic acid,phosphoric acid radicals, and also ammonium-and alkylammonium radicals.

Dyes suitable according to the invention include a variety of classes ofdyes having various chromophores, for example monoazo and disazo dyes,triarylmethane dyes, metal complex dyes, such as phthalocyanine dyes,quinophthalones and methine and azamethine dyes.

By way of example, reference may be made to the following Colour Indexnumbers:

Direct Yellow 4, 5, 11, 50, 127, 137, 147, 153; Acid Orange 7, 8; DirectOrange 15, 34, 102; Direct Red 81, 239, 252-255; Direct Violet 9, 51;Acid Blue 9, 86; Direct Blue 199, 218, 267, 273, 279, 281; Acid Black194, 208, 210, 221; Direct Black 19, 161, 170 and 171;

Basic Red 1, Basic Red 14, Basic Blue 7, Basic Blue 11, Basic Blue 26,Basic Violet 1, Basic Violet 4, Basic Violet 10 etc; reactive dyes suchas Reactive Red 120, Reactive Red 2 etc.

The dyes also include complexes of basic and acidic dyes and complexesof anionic and cationic dyes, for example the complex of chrysoidinebase and metanil yellow acid.

According to the invention, the dyes also include optical brightenerswhich are at least partially soluble in water.

In accordance with the definition, the organic dyes also includeUV-ray-absorbing compounds (UV stabilizers) which deactivate theabsorbed radiation in a nonradiative manner. Such compounds arefrequently used as UV absorbers in sunscreen compositions. These includederivatives of p-aminobenzoic acid, in particular its esters;salicylates, cinnamates, benzophenones, 2-phenylbenzimidazole-4-sulfonicacid and salts thereof, urocanic acid, salts thereof and esters thereof,benzoxazoles, benzotriazoles, benzylidenecamphor and its derivatives.

Also highly suitable are Colour Index dyes used in cosmetics, such as42045, 42051, 42080, 42090, 42735, 44045, 61585, 62045, 73015, 74180,bromothymol blue, caramel, 10316, 13015, 18690, 18820, 18965, 19140,45350, 47005, 75100, lactoflavin, 10020, 42053, 42100, 42170, 44090,59040, 61570, 75810, bromocresol green, 14270, 15510, 15980, 15985,16230, 20170, 40215, 14700, 14720, 14815, 15620, 16035, 16185, 16255,16290, 17200, 18050, 18130, 18736, 24790, 27290, 45100, 45220, 45380,45405, 45410, 45425, 45430, 75470, beetroot red, anthocyans, acid red195, black 20470, 27755, 28440, 50420, 42510, 42520, 45190 and 60730.

Depending on the color intensity of the dye, the microcapsule usuallycomprises at least 0.1% by weight, based on the hydrophilic solvent,preferably 1 to 50% by weight and in particular 5 to 20% by weight, ofat least one dye.

The capsule wall according to the invention consists essentially ofpolyurethane and/or polyurea. Preference is given to capsule walls whichessentially consist of polyurea, i.e. reaction products of NH₂group-containing reactants with di- and/or polyisocyanates.

Also suitable are di- and polyisocyanates, such as aliphatic,cycloaliphatic, araliphatic, aromatic and heterocyclic di- andpolyisocyanates, as are described by W. Siefken in Justus LiebigsAnnalen der Chemie, 562, pages 75 to 136, for example ethylenediisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylenediisocyanate, 1,12-dodecane diisocyanate, cyclobutane 1,3-diisocyanate,cyclohexane 1,3- and 1,4-diisocyanate and any mixtures of these isomers,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, asdescribed, for example, in DE-B 1 202 785 and U.S. Pat. No. 3,401,190,2,4- and 2,6-hexane-hydrotolylene diisocyanate, and any mixtures ofthese isomers, hexahydro-1,3- and -1,4-phenylene diisocyanate,perhydro-1,4′- and -4,4′-diphenylmethane diisocyanate, 1,3- and1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate, and anymixtures of these isomers, diphenylmethane 2,4′- and 4,4′-diisocyanate,naphthylene 1,5-diisocyanate, triphenylmethane 4,4′,4″-triisocyanate,polyphenylpolymethylene polyisocyanates, as obtained byaniline-formaldehyde condensation and subsequent phosgenation and aredescribed, for example, in GB patents 874 430 and 848 671, m- andp-isocyanatophenylsulfonyl isocyanates according to U.S. Pat. No.3,454,606, perchlorinated aryl polyisocyanates, as are described, forexample, in DE-B 1 157 601, polyisocyantes having carbodiimide groups,as are described in DE patent 1 092 007 (=U.S. Pat. No. 3,152,162),diisocyanates as described in U.S. Pat. No. 3,492,330, polyisocyanateshaving allophanate groups, as are described in GB patent 761 626 and thepublished NL patent application 7 102 524, polyisocyanates havingisocyanurate groups, as described, for example, in U.S. Pat. No.3,001,973, in the German patents 1 022 789, 1 222 067 and 1 027 394, andin German laid-open patents 1 929 034 and 2 004 048, polyisocyanateshaving urethane groups, as described, for example, in BE patent 752 261or in U.S. Pat. No. 3,394,164, polyisocyanates having acylated ureagroups according to German patent 1 230 778, polyisocyanates havingbiuret groups, as described, for example, in German patent 1 101 394 andin GB patent 889 050, polyisocyanates prepared by telomerizationreactions, as are described, for example, in U.S. Pat. No. 3,654,106,polyisocyanates having ether groups, as are mentioned, for example, inGB patents 965 474 and 1 072 956, in U.S. Pat. No. 3,567,763 and inGerman patent 1 231 688, reaction products of the abovementionedisocyanates with acetals according to German patent 1 072 385 andpolyisocyanates containing polymeric fatty acid radicals in accordancewith U.S. Pat. No. 3,455,883.

It is also possible to use the distillation residues having isocyanategroups which form during the industrial preparation of isocyanate,optionally dissolved in one or more of the abovementionedpolyisocyanates. It is also possible to use any mixtures of theabovementioned polyisocyanates.

Suitable modified, aliphatic isocyanates are, for example, those basedon hexamethylene 1,6-diisocyanate, m-xylylene diisocyanate,4,4′-diisocyanate dicyclohexylmethane and isophorone diisocyanate, whichhave at least two isocyanate groups per molecule.

Also suitable are, for example, polyisocyanates based on derivatives ofhexamethylene 1,6-diisocyanate with a biuret structure as described inDE-B 1 101 394, DE-B 1 453 543, DE-A 1 568 017 and DE-A 1 931 055.

It is also possible to use polyisocyanate-polyuretoneimines, as arise asa result of the carbodiimidization of hexamethylene 1,6-diisocyanatecontaining biuret groups with organophosphorus catalysts, whereprimarily formed carbodiimide groups react with further isocyanategroups to give uretoneimine groups.

It is also possible to use isocyanurate-modified polyisocyanates havingmore than two terminal isocyanate groups, e.g. those whose preparationon the basis of hexamethylene diisocyanate is described in DE-A 2 839133. Other isocyanurate-modified polyisocyanates can be obtainedanalogously thereto.

It is also possible to use mixtures of said isocyanates, e.g. mixturesof aliphatic isocyanates, mixtures of aromatic isocyanates, mixtures ofaliphatic and aromatic isocyanates, in particular mixtures whichoptionally comprise modified diphenylmethane diisocyanates.

The di- and/or polyisocyanates described here can also be used asmixtures with di- and polycarbonyl chlorides, such as sebacoyl chloride,terephthaloyl chloride, adipoyl dichloride, oxaloyl dichloride,tricarballyloyl trichloride and 1,2,4,5-benzenecarbonyl tetrachloride,with di- and polysulfonyl chlorides, such as 1,3-benzenesulfonyldichloride and 1,3,5-benzenesulfonyl trichloride, phosgene and withdichloro- and polychloroformic esters, such as 1,3,5-benzenetrichloroformate and ethylene bischloroformate.

Preferred isocyanates are biuretic hexamethylene diisocyanate,optionally in a mixture with 4,4′-diphenylmethane isocyanate andoptionally 2,4-diphenylmethane isocyanate, trimerized hexamethylenediisocyanate optionally in a mixture with 4,4′diphenylmethanediisocyanat and optionally 2,4-diphenylmethane diisocyanate.

Further preferred diisocyanates are the alkylbenzene diisocyanates andalkoxybenzene diisocyanates given in DE-A 3 105 776 and 3 521 126,including those in the form of their biuret isocyanate uretdioneoligomers.

Preferred di- or polyisocyanates are 4,4′-diphenylmethane diisocyanate,the mixtures of monomeric diphenylmethane diisocyanates and oligomericdiphenylmethane diisocyanates (polymer MDI), tetramethylenediisocyanate, tetramethylene diisocyanate trimers, hexamethylenediisocyanate, hexamethylene diisocyanate trimers, isophoronediisocyanate trimer, 4,4′-methylenebis(cyclohexyl) diisocyanate,xylylene diisocyanate, tetramethylxylylene diisocyanate, dodecyldiisocyanate, lysine alkyl ester diisocyanate, where alkyl is C₁ to C₁₀,2,2,4- or 2,4,4-trimethyl-1,6-hexamethylene diisocyanate,2-butyl-2-ethylpentamethylene diisocyanate, 1,4-diisocyanatocyclohexaneor 4-isocyanatomethyl-1,8-octamethylene diisocyanate.

Particular preference is given to di- or polyisocyanates having NCOgroups of varying reactivity, such as 2,4-tolylene diisocyanate(2,4-TDI), 2,4′-diphenylmethane diisocyanate (2,4′-MDI),triisocyanatotoluene, isophorone diisocyanate (IPDI),2-butyl-2-ethylpentamethylene diisocyanate, 2-isocyanatopropylcyclohexylisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate,1,4-diisocyanato-4-methylpentane, 2,4′-methylenebis(cyclohexyl)diisocyanate and 4-methylcyclohexane 1,3-diisocyanate (H-TDI).Particular preference is also given to isocyanates whose NCO groups areinitially equally reactive, but in which a reactivity decrease in thecase of the second NCO group can be induced as a result of the firstaddition of an alcohol or amine onto an NCO group. Examples thereof areisocyanates whose NCO groups are coupled via a delocalized electronsystem, e.g. 1,3- and 1,4-phenylene diisocyanate, 1,5-naphthylenediisocyanate, diphenyl diisocyanate, tolidine diisocyanate or2,6-tolylene diisocyanate.

In addition, it is possible to use, for example, oligo- orpolyisocyanates which can be prepared from said di- or polyisocyanatesor mixtures thereof by linking by means of urethane, allophanate, urea,biuret, uretdione, amide, isocyanurate, carbodiimide, uretonimine,oxadiazinetrione or iminooxadiazinedione structures.

NH₂-containing reactants according to the invention are: hydrazine,guanidine and salts thereof, hydroxylamine, di- and polyamines andaminoalcohols. These compounds can be used in pure form or as mixtureswith one another. A preferred guanidine salt is guanidine carbonate. Ifguanidine salts of strong acids are used, the addition of a base isrequired.

Suitable amines are generally polyfunctional amines in the molecularweight range from 32 to 500 g/mol, preferably from 60 to 300 g/mol,which contain at least two amino groups chosen from the group of primaryand secondary amino groups. Examples thereof are diamines, such asdiaminoethane, diaminopropanes, diaminobutanes, diaminohexanes,piperazine, 2,5-dimethyl-piperazine,amino-3-aminomethyl-3,5,5-trimethylcyclohexane (isophoronediamine,IPDA), 4,4′-diaminodicyclohexylmethane, 1,4-diaminocyclohexane,aminoethylethanolamine, hydrazine, hydrazine hydrate or triamines suchas diethylenetriamine or 1,8-diamino-4-aminomethyloctane.

The amines can also be used in blocked form, e.g. in the form of thecorresponding ketimines (see e.g. CA-A-1 129 128), ketazines (cf. e.g.U.S. Pat. No. 4,269,748) or amine salts (see U.S. Pat. No. 4,292,226).

Examples of aminoalcohols are ethanolamine and triethanolamine. Inprinciple, water can also act as reactant by, as a result of additiononto an NCO group and subsequent CO₂ elimination, generating an aminogroup which can then react with an NCO group with crosslinking.

Preferred NH₂-carrying reactants are diamines, particularly preferablyaliphatic C₂-C₆-diamines, such as ethylenediamine andhexamethylenediamine.

The amount of isocyanates to be used according to the invention varieswithin the scope customary for interfacial polyaddition processes. Thus,20 to 150% by weight, preferably 40 to 150% by weight, of isocyanate areused based on the discontinuous phase provided for the encapsulation(hydrophilic solvent+water-soluble substance). Good shear stabilities ofthe capsules can be observed from amounts as low as 40% by weight.Amounts above 150% by weight are possible, but do not generally lead tomore stable capsule walls.

The theoretical amount of the reactants necessary for wall formation iscalculated from a) the content of reactive amino and/or hydroxyl groupsof the reactant component used. These quantitative ratios are usuallyexpressed by equivalent weights.${{{{Equivalent}\quad{weight}_{isocyanate}} = {\frac{42}{{{NCO}\quad{content}}{*)}} \times 100}}\quad{*)}} = {{e.g.\quad{to}}\quad{be}\quad{determined}\quad{titrimetrically}\quad\left( {{DIN}\quad 53\quad 185} \right)}$${{Equivalent}\quad{weight}_{reactant}} = \frac{{molecular}\quad{weight}_{reactant}}{{number}\quad{of}\quad{reactive}\quad{groups}\quad{in}\quad{the}\quad{moelcule}}$

Reaction of all of the NCO groups present in the oil phase requires atleast the theoretically equal number of NH₂ and/or OH groups. It istherefore advantageous to use the isocyanate and the reactant in theratio of their equivalent weights. It is, however, likewise possible todeviate from the stoichiometrically calculated amount of reactant eitherdownward since, during interfacial polyaddition processes, a secondaryreaction of the isocyanate with the water present in excess cannot beruled out, or to use an excess of the reactant component because such anexcess is uncritical.

In particular, therefore, the reactants are used in an amount between 50and 150% by weight of the theoretically calculated amount. This amountis preferably between 50 and 100% by weight, based on the theoreticallycalculated amount.

The present invention further provides a process for the preparation ofthe microcapsule dispersion according to the invention, which comprisespreparing an emulsion of the hydrophilic solvent in the-hydrophobicsolvent using a surface-active substance, where the hydrophilic phasecomprises the water-soluble organic substance and the OH or NH₂group-carrying reactants which react with di- and/or polyisocyanategroups, and adding di- and/or polyisocyanates to the emulsion.

In order to obtain a stable emulsion, surface-active substances, such asprotective colloids and/or emulsifiers, are required. Usually,surface-active substances which mix with the hydrophobic phase are used.

Preferred protective colloids are linear block copolymers with ahydrophobic structural unit of length ≧50 Å, alone or in mixtures withother surface-active substances. The linear block copolymers are givenby the formulaC_(w)B—A—B_(y)_(x)D_(z)in which w is 0 or 1, x is 1 or more, y is 0 or 1 and A is a hydrophilicstructural unit, having a solubility in water at 25° C. of ≧1% by weight(>10 g/l) and a molecular weight of from 200 to 50 000, which is bondedcovalently to the B blocks, and B is a hydrophobic structural unithaving a molecular weight of from 300 to 60 000 and a solubility inwater at 25° C. of <1% by weight and can form covalent bonds to A; andin which C and D are end groups which, independently of one another, maybe A or B. The end groups may be identical or different and areindependent of the preparation process.

Examples of hydrophilic groups are polyethylene oxides,poly(1,3-dioxolane), copolymers of polyethylene oxide orpoly(1,3-dioxolane), poly(2-methyl-2-oxazoline),poly(glycidyltrimethylammonium chloride), polymethylene oxide.

Examples of hydrophobic groups are polyesters in which the hydrophobicpart is a steric barrier ≧50 Å, preferably ≧75 Å, in particular ≧100 Å.The polyesters are derived from components such as 2-hydroxybutanoicacid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 2-hydroxycaproicacid, 10-hydrodecanoic acid, 12-hydroxydodecanoic acid,16-hydroxyhexadecanoic acid, 2-hydroxyisobutanoic acid,2-(4-hydroxyphenoxy)propionic acid, 4-hydroxyphenylpyruvic acid,12-hydroxystearic acid, 2-hydroxyvaleric acid, polylactones fromcaprolactone and butyrolactone, polylactams from caprolactam,polyurethanes and polyisobutylenes.

The linear block copolymers contain both hydrophilic units andhydrophobic units. The block polymers have a molecular weight above 1000 and a length of the hydrophobic moiety of ≧50 Å calculated accordingto the law of cosines. These sizes are calculated for the extendedconfiguration, taking into consideration the bond lengths and anglesgiven in the literature. The preparation of these units is generallyknown. Preparation processes are, for example, condensation reaction ofhydroxy acid, condensations of polyols, such as diols, withpolycarboxylic acids, such as dicarboxylic acids. Also suitable is thepolymerization of lactones and lactams, and the reaction of polyols withpolyisocyanates. Hydrophobic polymer units are reacted with thehydrophilic units, as generally known, for example by condensationreaction and coupling reaction. The preparation of such block copolymersis described, for example, in U.S. Pat. No. 4,203,877, to whichreference is expressly made. The proportion of linear block copolymersis preferably 20-100% by weight of the total amount of surface-activesubstance used.

Suitable surface-active substances are also the emulsifiers customarilyused for water-in-oil emulsions, for example

-   -   C₁₂-C₁₈-sorbitan fatty acid esters,    -   esters of hydroxystearic acid and C₁₂-C₃₀-fatty alcohols,    -   mono- and diesters of C₁₂-C₁₈-fatty acids and glycerol or        polyglycerol,    -   condensates of ethylene oxide and propylene glycols,    -   oxypropenylated/oxyethylenated C₁₂-C₂₀-fatty alcohols,    -   polycyclic alcohols, such as sterols,    -   aliphatic alcohols with a high molecular weight, such as        lanolin,    -   mixtures of oxypropylenylated/polyglycerylated alcohols and        magnesium isostearate,    -   succinic esters of polyoxyethylated or polyoxypropylenated fatty        alcohols,    -   the lanolates and stearates of magnesium, calcium, lithium, zinc        and aluminum, optionally as a mixture with hydrogenated lanolin,        lanolin alcohol, or stearic acid or stearyl alcohol.

Emulsifiers of the Span® series (ICI Americas, Inc.) have provenparticularly advantageous. These are cyclized sorbitol, sometimespolyesterified with a fatty acid, where the base structure can also besubstituted by further radicals known from surface-active compounds, forexample by polyoxyethylene. Examples which may be mentioned are thesorbitan esters with lauric, palmitic, stearic and oleic acid, such asSpan 80 (sorbitan monooleate) and Span 60 (sorbitan monostearate).

In a preferred embodiment, oxypropylenated/oxyethylenated C₁₂-C₂₀-fattyalcohols are used as mixing component with further surface-activesubstances. These fatty alcohols usually have 3 to 12 ethylene oxide orpropylene oxide units.

Preference is given to using C₁₂-C₁₈-sorbitan fatty acid esters asemulsifier. These can be used individually, in their mixtures and/or asmixtures with other abovementioned types of emulsifier. The proportionof sorbitan fatty acid esters is preferably 20-100% by weight of thetotal amount of surface-active substance used.

In a preferred embodiment, a mixture of surface-active substancescomprising the above-defined linear block copolymers andC₁₂-C₁₈-sorbitan fatty acid esters is chosen.

Particularly preferably, a mixture of surface-active substancescomprising the linear block copolymers C₁₂-C₁₈-sorbitan fatty acidesters and oxypropenylated/oxyethylenated C₁₂-C₂₀-fatty alcohols arechosen.

Preference is given to those mixtures comprising 20 to 95% by weight, inparticular 30 to 75% by weight, of linear block copolymer and 5 to 80%by weight, in particular 25 to 70% by weight, of C₁₂-C₁₈-sorbitan fattyacid esters, based on the total amount of surface-active substance. Theproportion of oxypropylenated/oxyethylenated C₁₂-C₂₀-fatty alcohol ispreferably 0 to 20% by weight.

Particular preference is given to mixtures of surface-active substancescomprising essentially 40 to 60% by weight of linear block copolymer, 30to 50% by weight of C₁₂-C₁₈-sorbitan fatty acid esters and 2 to 10% byweight of oxypropylenated/oxy-ethylenated C₁₂-C₂₀-fatty alcohols, basedon the total amount of surface-active substance.

The optimum amount of surface-active substance is influenced firstly bythe surface-active substance itself, and secondly by the reactiontemperature, the desired microcapsule size and the wall materials. Theoptimally required amount can be readily determined by simple serialexperiments. The surface-active substance is generally used in an amountof from 0.01 to 10% by weight, preferably 0.05 to 5% by weight and inparticular 0.1 to 2% by weight, based on the hydrophobic phase.

To prepare the microcapsules according to the invention, according to apreferred embodiment, a solution of water-soluble organic substance andOH- or NH₂-carrying reactant in the hydrophilic solvent can be added tothe hydrophobic solvent. With the help of the surface-active substance,a stable emulsion is prepared with stirring. According to a likewisepreferred variant, the water-soluble organic substances and the reactantare added only to the stable emulsion or during the emulsifying step.The isocyanate can then be metered in to such an emulsion. Generally,this starts the interfacial polyaddition or condensation and thus theformation of the wall.

The interface reaction can proceed, for example, at temperatures in therange from −3 to +70° C., but preference is given to working at 0 to 25°C.

Depending on the size of the capsules to be prepared, the nucleatingmaterial is dispersed in a known manner. For the preparation of largecapsules, dispersion using effective stirrers, in particular propelleror impeller stirrers, suffices. Small capsules, particularly if the sizeis to be less than 50 μm, require homogenizing or dispersing machines,it being possible for these devices to be provided with or withoutforced-flow equipment.

The homogenization can also be carried out using ultrasound (BransonSonifier II 450). For homogenization by means of ultrasound, suitableequipment is, for example, that described in GB 2250930 and U.S. Pat.No. 5,108,654.

The capsule size can be controlled via the speed of the dispersionapparatus/homogenization apparatus and/or using the concentration of theprotective colloid or via the molecular weight thereof, i.e. via theviscosity of the aqueous continuous phase within certain limits. In thisconnection, as the speed increases up to a limiting speed, the size ofthe dispersed particles decreases.

In this connection, it is important that the dispersion devices are usedat the start of capsule formation. In the case of continuously operatingdevices with forced-flow, it is advantageous to pass the emulsionthrough the shear field a number of times.

Using the process according to the invention, it is possible to preparemicrocapsule dispersions with a content of from 5 to 50% by weight ofmicrocapsules. The microcapsules are individual capsules. If suitableconditions are chosen during the dispersion it is possible to preparecapsules with an average particle size in the range from 0.5 to 50 μmand above. Preference is given to capsules with an average particle sizeof from 0.5 to 50 μm, in particular up to 30 μm. The average particlediameter is the number-average particle diameter, determined byquasielastic, dynamic light scattering. It is usually determined using aCoulter N4 Plus particle analyzer from Coulter Scientific Instruments.The size distribution of the capsules is particularly advantageouslyvery narrow.

The microcapsule dispersions according to the invention can beincorporated into cosmetic compositions in a known manner. Incorporationinto the cosmetic composition takes place by the procedures customaryfor this purpose, usually by stirring and homogenizing into the otherconstituents of the cosmetic composition.

Examples of cosmetic compositions which are formulated as decorativecosmetic composition are compositions for the treatment of facial skin,in particular in the eye area, such as kohl pencils, eyeliner pencils,eyebrow pencils, eyeshadows, cream blusher, powder blusher, foundation,make-up, e.g. stage make-up, lipsticks.

In the case of cosmetic compositions which consist exclusively of oilsor fats, in particular those which have a solid form, e.g. pencils, suchas kohl pencils, eyeliner pencils, eyebrow pencils, stick stage make-up,lipsticks and the like, and in the case of powder or fine powdercosmetic compositions, such as eyeshadows and cream blusher or loosepowder blusher, preference is given to using microcapsule dispersions.

The amount of microcapsules in the cosmetic composition is governedprimarily by the desired color impression which the decorative cosmeticcomposition is to have. Depending on the nature of the cosmeticcomposition and the desired color impression, the content ofmicrocapsules in the cosmetic composition is in the range from 0.1 to50% by weight, based on the total weight of the cosmetic composition.

EXAMPLE 1

A solution of 1.5 g of Span® 80 (sorbitan monooleate), 0.3 g ofCremophor® A6 [75% by weight of ceteareth-6 (ethoxylated cetyl alcohol),25% by weight of stearyl alcohol, BASF] and 2.1 g of Arlacel® P135(PEG-30 dipolyhydroxystearate, Atlas Chemie) in 860 g of Miglyol®(decanoyl/octanoyl glyceride; Hüls) 812 was introduced into acylindrical 2 l stirred vessel. A dispersing apparatus (Turrax 45 N,from Jahnke & Kunkel) was used to prepare a water-in-oil emulsion byadding a solution of 6.7 g of ethylenediamine and 4 g of Cochenille RedA (E124; C.I. 162 55) in 80 g of water at a rotary speed of 6 000 rpm.The resulting emulsion was cooled to 2° C. in an ice bath at a stirrerspeed of 1 000 rpm. With ice cooling, a solution of 23 g of Basonat® LR8528 (polyfunctional tolylene diisocyanat adduct, 75% strength by weightin ethyl acetate; BASF) in 300 g of Miglyol was added at the samestirring speed over the course of 300 min. When the addition wascomplete, the dispersion was heated to room temperature and stirred fora further 180 min. The resulting dispersion was red-milky and, accordingto microscopic assessment, comprised individual capsules ofpredominantly 1 to 5 μm in diameter. The viscosity was 47.5 mPas and thesolids content was 11% by weight.

The viscosities were measured in accordance with ISO 3219 (DIN 53019)using a Physica MC20 viscometer in measurement system 21 at a shearspeed of 100 s⁻¹ and a temperature of 23° C. The capsule diameter wasdetermined optically at 400× magnification using a microscope from Leitz(Diaplan 101/107).

EXAMPLE 2

A microcapsule dispersion was prepared analogously to example 1, the dyeused being 4 g of Reactive Red 120. The resulting dispersion wasred-milky and, according to microscopic assessment, comprised individualcapsules of predominantly 1 to 5 μm in diameter. The viscosity was 43.9mPas and the solids content was 11% by weight.

EXAMPLE 3

A microcapsule dispersion was prepared analogously to example 1, the dyeused being 4 g of Reactive Red 2. The resulting dispersion was red-milkyand, according to microscopic assessment, comprised individual capsulesof predominantly 1 to 5 μm in diameter. The viscosity was 45.2 mPas andthe solids content was 11% by weight.

EXAMPLE 4

Analogous to example 1, the aqueous solution used being a mixture of 64g of H₂O and 16 g of ethanol. The resulting dispersion was red-milkyand, according to microscopic assessment, comprised individual capsulesof predominantly 1 to 5 μm in diameter. The viscosity was 50.2 mPas andthe solids content was 11% by weight.

1. A microcapsule dispersion comprising microcapsules having a capsulecore comprising water-soluble dyes, and a capsule coating whichessentially consists of polyurethane and/or polyurea, in a hydrophobicsolvent which consists of 50 to 100% by weight of glycerol ester oilsand 0 to 50% by weight of solvents miscible with glycerol ester oils. 2.A microcapsule dispersion as claimed in claim 1, wherein the capsulecoatings essentially consist of reaction products of NH₂ group-carryingreactants with di- and/or polyisocyanates.
 3. A microcapsule dispersionas claimed in claim 1 or 2, wherein the hydrophobic solvent are glycerolester oils.
 4. A microcapsule dispersion as claimed in claim 1, whereinthe capsule core comprises water as hydrophilic solvent.
 5. A processfor the preparation of a microcapsule dispersion as in claim 1, whichcomprises preparing an emulsion of the hydrophilic solvent in thehydrophobic solvent using a surface-active substance, where thehydrophilic phase comprises the water-soluble dyes and the OH or NH₂group-carrying reactants which react with di- and/or polyisocyanategroups, and adding di- and/or polyisocyanates to the emulsion.
 6. Aprocess as claimed in claim 5, wherein the surface-active substance usedis a linear block copolymer with a hydrophobic structural unit with alength of more than 5 nm (50 Å), which is defined by the followingformula:C_(w)B-A-B_(y)_(x)D_(z) in which A is a hydrophilic structural unitwhich has a solubility in water at 25° C. of 1% or more, has a molarmass of from 200 to 50 000, and is chosen such that it is bondedcovalently to B; B is a hydrophobic structural unit which has a molarmass of from 300 to 60 000, a solubility in water at 25° C. of less than1% and can be bonded covalently to A; C and D are end groups which maybe A or B and the same group or different groups; w is 0 or 1; x is 1 oran integer >1; y is 0 or 1, and z is 0 or
 1. 7. A process as claimed inclaim 6, wherein the linear block copolymer is a 12-hydroxystearic acidblock copolymer.
 8. A process according to claim 5, wherein thesurface-active substance used is C₁₂-C₁₈-sorbitan fatty acid ester.
 9. Aprocess as claimed in claim 5, wherein the surface-active substance usedis a combination comprising C₁₂-C₁₈-sorbitan fatty acid esters andlinear block copolymers with a hydrophobic structural unit with a lengthof more than 5 nm (50 Å), which is defined by the following formula: C_(w)B-A-B_(y)_(x)D_(z) in which A is a hydrophilic structural unitwhich has a solubility in water at 25° C. of 1% or more, has a molarmass of from 200 to 50 000, and is chosen such that it is bondedcovalently to B; B is a hydrophobic structural unit which has a molarmass of from 300 to 60 000, a solubility in water at 25° C. of less than1% and can be bonded covalently to A; C and D are end groups which maybe A or B and the same group or different groups; w is 0 or 1; x is 1 oran integer >1; y is 0 or 1, and z is 0 or 1.